just powered up my QMX+. Software loaded nicely and seems to be fine. I can change bands an hear some noise in the earphones. But no receive at all. I tried to send a signal from another rig and did not hear anything at all on the QMX. Is there something I overlooked in the setup or did I make a mistake in the build.

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I did not look into the tools af chapter 8 as I totally ignore how to use PuTTY ( I did not eben know about it)

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Martin

DK3UW

Martin,

Did you put in the jumper from the BNC center pin trace to the T507?

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73, Dan? NM3A

Easy to miss!

Wasted half a day tracing signals.

Yes the jumper is there

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Martin

DK3UW

I managed to get that PuTTY to start.

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Audio

RF Filter Sweep

image Sweep

SWR Sweep with dummy load. That looks ok to me.

LPF Do I understand it correctly that on 3.5 Mhz I am 20 db down ?

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Test ADC I/Q not sure what that means

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Diagnostics

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I had an issue with the 2 buttons as I soldered them on the wrong side of the board and had to remove them. I later checked R 301 and 302 and the switches seemed to work.? I have not installed a paddle yet.

Sorry for dividing this up into so many posts. Does anyone have a tip where to look to get the receiver going.

By the was the 2 buttons do work if I go into the menue.

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Martin

DK3UW

I think I have a problem at? 514 as I measure ground on both sides. Looking at the bottom to me it looks like both wires are soldered to the ground plane. Can someone having an unmounted QMX + post a picture of the underside of the board where L 514 will be positioned ?

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Martin

DK3UW

sorry L 514

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Martin

DK3UW

Hi Martin,

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Will you be able to use the attached photo?

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73, Aki, JO4MTH

HI Martin,

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Your transmit chain appears to be functional (good SWR and LPF tests), but the receive chain is broken (bad Audio, Image, and RF filter tests).? ?

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The ADC I/Q tests shows that the ADC (PCM1804) is alive, but possibly defective.? One channel (red trace) is apparently being overdriven rail-to-rail, which is far from normal.? The 8388608 (decimal) is close to the largest positive value that you could get out of a 24-bit ADC.? ?The other channel (yellow trace) has values that are well within range.? This I/Q imbalance would trash any receive chain operation.? The I/Q imbalance could arise in the PCM1804 circuit or closer to the antenna.

The wiki section titled "QMX QMX_plus Audio PCM1804" (/g/QRPLabs/wiki/37111) has a description of some diagnostics you could try to determine where in the receive path the problem lies.? It also suggests where on the board you might look for bad solder joints, solder bridges, etc.

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Good luck,

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Carlos - KJ6ST

Thanks Aki, that helps

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Martin

DK3UW

maybe I have overlooked it somewhere but I would like to find some kind of document explaining how the QMX concept works. Also I would like something like for the QCX witrh voltages at various points for further troubleshooting. And finally Cheatsheet with the functions of the QMX.

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Martin

DK3UW